Massachusetts Institute of Technology

Steven Dubowsky

Moustapha Hafez

Matthew Lichter

Peter Weiss

Andreas Wingert

Ferenc A Jolesz

Daniel F Kacher

Seung J Lee

Haoyong Yu

Guillaume Morel

Amy M Bilton

System for establishing a surface shape. The system includes a compliant substrate including the surface and having a reverse side, and a plurality of discrete actuators engaging the reverse side and arranged in a selected pattern to control the surface shape as individual discrete activators are activated. It is preferred that the actuators have multiple discrete stable states of elongation. A particularly preferred embodiment uses actuators that are binary with two stable states of elongation.

System for discretely actuated solar mirrors

The system of the present invention includes an actuator having at least two electrodes, an elastomeric dielectric film disposed between the two electrodes, and a frame attached to the elastomeric dielectric film. The frame provides a linear actuation force characteristic over a displacement range. The displacement range is preferably the stroke of the actuator. The displacement range can be about 5 mm and greater. Further, the frame can include a plurality of configurations, for example, at least a rigid members coupled to a flexible member wherein the frame provides an elastic restoring force. In preferred embodiments, the rigid member can be, but is not limited to, curved beams, parallel beams, rods and plates. In a preferred embodiment the actuator can further include a passive element disposed between two flexible members such as, for example, links to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. Further, the actuator can include a plurality of layers of the elastomeric dielectric film integrated into the frame. The elastomeric film can be made of different materials such as, for example, acrylic, silicone and latex.

Dielectric elastomer actuated systems and methods

The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as &#xb1;20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.

Elastomeric actuator devices for magnetic resonance imaging

A wheel base or mobile platform providing omnidirectional motion and control. At least two offset wheel assemblies are coupled to a platform that supports a load. Each offset wheel assembly has two wheels that share a common axis and a mechanical link that is pivotally coupled to a pivot point on the rigid platform and supports the two wheels in such a manner that the common axis is displaced from the pivot point. The common axis of the wheels is free to rotate about an axis parallel to the planes of rotation of the wheels. The platform may be turned in any direction specified by a user from any instantaneous configuration or velocity in accordance with a method uniquely specifying a torque to be applied to each of the wheels while each of the wheels is in rolling motion.

Omnidirectional vehicle with offset wheel pairs

An elegant, cost-effective apparatus and method is disclosed for compensating the effect of joint friction in manipuulators. The invention uses a six axis wrench sensor (also called a force/torque sensor) mounted between the manipulator and a reference body upon which it is supported. From the base wrench measurements, for rotary joints, the joint torques are estimated. The estimation apparatus uses Newton-Euler relations of successive link bodies. The estimated torque is fed back through a torque controller, that virtually eliminates friction and gravity effects. A position control loop encloses the torque controller and provides it with desired torques computed from measured position errors. For linear joints, appropriate forces are estimated. Coupled to link position sensors and the wrench sensor, is a gravity compensator, which generates a dynamic wrench signal that corresponds to the gravity compensated dynamic component of the base wrench signal, based on the position signals and the base wrench signal. Coupled to the gravity compensator and the position sensors is a joint analyzer, which generates a signal that corresponds to the gravity compensated torque that is actually applied to the link at the rotary joint, based on the dynamic wrench signal and the position signals. Both torques at rotary joints and forces at linear joints are estimated by the apparatus. Multiple and single joint manipulators can be evaluated. The achieved precision is substantially greater than for conventional methods and approaches the resolution of the Puma's encoders.

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Steven Dubowsky